The influence of chromium doping on the physical properties of ZnO thin films, deposited by the chemical spray technique, is presented. In particular, we have studied the chemical stability of ZnO:Cr as a function of chromium concentration on the starting solution. Although, according to x-ray diffraction measurements, the Cr incorporation into the films remains below 1 at. % for all the concentrations used, a notorious influence is observed on the etching rate, the crystalline orientation, and the surface morphology. The resistivity of the as-deposited films is of the order of 10(4) fl CM. After a vacuum annealing at 400 degreesC its magnitude decreases at around 10(3) fl cm. The films show a high transmittance, about 80% at 550 nm, irrespective of the Cr concentration used in the starting solution.